RADIO NOTES

Dominion, Volume 25, Issue 81, 30 December 1931, Page 14

RADIO NOTES

By

“ETHER"

THE BEST AERIAL Weakness of a Frame OUTDOOR TYPE’S MERITS i Several readers want to know what is the best type of aerial, some asking whether anything is to be gained by using a frame aerial. The matter probably interests most listeners, especially those who use sets of a fairly modest type. In the first place it is well to mention that as far as collecting energy is concerned a frame aerial is the world s worst aerial. Ten feet of wire hung along the wall is better than many frame aerials. Anybody anxious to have a good frame aerial might well contemplate making one with sides fifteen feet long. Even then a good outdoor aerial will beat it. The only merit in a frame aerial is its directional effects. In these days of highly selective super-heterodyne receivers that attribute is unwanted. ’

Ambitious users of one-valve sets and crystal sets must remember that a good aerial is money well spent. It will give results equal to-at least an extra valve. There are two main types of aerials. One type consists of a horizontal span of wire with- a downlead at one end. The other type consists of a horizontal span with a downlead from the centre. The former is called an inverted “L” aerial, and the latter a “T” aerial. In practice there is not much to choose between the two types. Experiments show, however, that the “T” aerial gives slightly better results when its horizontal length is over fifty feet long. In either , type of aerial practically no benefit is obtained, by using more than one wire. It is worth realising nevertheless that provided the two wires are spaced some fifteen feet apart results will be roughly ten per cent, better. Usually the extra cost of stronger masts and gear makes it cheaper to add another valve and get several hundred per cent, better results. Height a Deciding Factor.

The factor in almost any type of aerial that produces results is height.. The higher an aerial the better. Users of crystal sets in* the country, as well as users of one .or two-valve , sets should try to erect an aerial between masts fifty feet high. Up to about that height every toot makes quite an im< provement. Above that height results improve only slowly. An extra viilve works out as the cheaper proposition above an aerial height of fifty feet. Moreover, the length of an aerial makes a considerable difference. A horizontal span of 100 feet is none too long. Additional length, however, brings in its train reduced selectivity. There also comes a time when the aerial'resonates. to the broadcast wave band without a coll at all. This makes tuning impossible. It is unwise to make,the horizontal span much longer than 300 feet. There are several points to attend to whatever type of aerial is used. The aerial should be kept clear of all metal objects such as tin roofs, gutters, and Water jiipes. It should not be allowed to come dose to trees. This refers to the down lead as well. Trees shield the aerial. In the summer they may account for far greater losses than might be expected. The ideal aerial would be one erected in a treeless and houseless plain with its horizontal span slung across a lake or pond. Unless some mention is made of earths it is possible to erect a perfect aerial and still receive very poor results. A good aerial must have a good earth. In the case of the aerial slung aerdss a pond a perfect earth may be obtained by running several copper wires in the water immediately under the aerial. A copper sheet 10ft. by 10ft. submerged in the water near the aerial will be almost as good. Either of these two suggestions make excellent earths if they are buried under an aerial slung across laiicl.

Question of the Earth. , Most of us. are unable to make much choice in the matter of an earth. Usually our choice lies between a piece of water piping driven into the ground and a connection to the water mains themselves. Never make an earth to a gas main. It is a bad earth aiid dangerous. Of the two courses mentioned the main water mains make the better earth;- Be sure to connect to a rising main—that Is, a pipe, directly connected to the main supply. Earth clips for the common size of pipes in use may be bought for sixpence or so. Use stout wire for. the earth connection. If the choice lies between a long earth lead to a water mains or one only a few feet long to a pipe driven into the ground possibly the latter will be. the better. Try both in turn and see which is the best. Where a pipe is used driven into the ground choose a damp spot. In dry weather a few buckets of water may well be poured over it. Those people fortunate enough to own, a multi-valve set of modern make can use almost anything for an aerial. A piece of wire ten feet long will serve them in many cases. These notes are not for them—nevertheless they may obtain better results if they have time to put sqme of these facts to practical use.

LURING TOURISTS . To encourage tourists to visit the Old Country, the Travel Association of ' Great Britain and Ireland has arranged to broadcast talks on the attractions of' the British Isles from 300 U.S. and Canadian stations during the winter months. Several European stations are also being enlisted for the good work, one of them being Radio-Lyons.

RADIO GRAMOPHONES Prophecies for the Future LONG RECORD-PLAYING In no technical .matter is ,it more fascinating to endeavour to .take a peep into j;he future'than it is in the matter of the radio-gram, writes J. F. Couiffan, in “Popular Wireless. ’ Few of us are able to recall clearly the time when the radip-gram was not; and when the old-time acoustical giainophone was more or less looked down upon on all sides as,a raucous noisegenerator. All this sort of attitude, of course, has changed since the improvements .which have come about in the art and science of gramophonics during recent years, and, most Particularly, since the advent of the radio-gram.

Imminent Improvements. Yet, gramophones, and even radiograms,’ still have their critics. As ..the latter people insistently point out, modern record-playing instruments, although they have reached a very highdegree of perfection, are still deficient in one respect. The records which they use.-are not long-lasting enough, .By that ! mean,, of course, that their playing tifne is too short, although, even so far as actual durability goes, there is no-,doubt that there is -still room for improvement. ■ . Now that:.the radio-gram and its acoustical confrere have reached such a high and truly excellent degree of tonal performance, there is going on an eager search for what may be termed refinements in radio-gramophony. Thus we have the electrically driven motor which obviates the bugbear of winding up. Strangely enough, the electric motor was used in the very early days of Edison’s original phonographs, but, owing to the necessity of having.to work it off storage batteries, it was given up as soon as a reliable clockwork motor was perfected. Needles, which play many records without wearing too much, are common articles nowadays, and radiograms embodying ingenious mechanisms for record changing and selecting are becoming almost daily more in evidence. ■ ' v

Such improvements and refinements, however, are not in the nature of radical changes in gramophone and radiogram design. Nor are the many suggestions toward the production of long-playing records which have Been put forward ever since Mr. Pemberton Billing, in 1919.. took out several patents for a long-playing record. / Runs ‘for an Hour.

There is no doubt whatever that the radio-gram of the future —for acoustical reproduction will entirely give way to electrical playing sooner or laterwill be one which will play for an hour without needing attention. You will be able to obtain huge chunks of opera on a record. Two records will be able to hold an entire Shakespearean play or a modern revue, whilst a long orchestral symphony in three movements will be able to be stored away very comfortably without at all straining the capacity of one record. Such, I imagine, will be the state of affairs in the world of radio-gramo-phony in, say, twenty years’ time. And tha.t, of course, is not taking into consideration the close conjunction which is bound to be made very shortly between the home cinema and the radiogram. : . ‘ •'? ' Very little imagination is needed to visualise the above statements. Already the material, the knowledge, and the means for effecting them are at hand. It is only a question, more or less, of who is going to be the first to begin.' There seems to be little doubt that the record of the present-day—the composition disc—will go. Perhaps, of course, it may not, if only in view of the enormous amount of capital which has been sunk in the manufacture of these discs. In such an instance, the radio-gram of the future will be a combination affair—one which is able to play the short disc records by means of a needle and pick-up, and. also, the long-playing celluloid ribbon records—for such the future records will be.

TRANSMITTER ADRIFT Professor Moltehanov, of the Soviet Arctic Institute, has designed a radio transmitter which will automatically broadcast meteorological data from the Behring Straits when cast adrift on a buoy. The first test will be made next spring.